Internal combustion engines which are not loaded must operate, when idling, at predetermined idling speeds. These idling speeds are not necesarily always the same, but may change with operating conditions, and environmental conditions in which the engine operates, for example temperature. Idling speed control systems have previously been proposed, see the referenced U.S. Pat. No. 4,359,991, HAUBNER et al., the disclosure of which is hereby incorporated by reference; and see, for example, German Patent Disclosure Document DE-OS No. 31 24 496, HAUBNER, likewise assigned to the assignee of the present application. The control effect of an engine operating controller must be matched to the required performance of the engine, for example to so control engine operation that riding comfort and freedom from shock and vibration of occupants of an automotive vehicle, in which such an engine may be installed, are considered. The control behavior of the controllers thus must be matched to particular requirements, including special conditions which may arise in the operation of the engine or in view of environmental conditions. The operating changes can be controlled, for example, by specifically controlling the characteristics of engine controllers, particularly characteristics of integrators, differentiators, or proportional controllers, or elements therein. Thus, the proportional control, integrating or differential control based on input parameters, can be modified. The various characteristics can be interrelated with respect to each other, for example in dependence on operating or environmental parameters, such as ambient temperature. Various types of systems are known, which are more or less complex, in order to match the behavior of the controller to predetermined parameters, and external and operating conditions of the engine. Usually, the requirement of material and networks in substantial. The reaction time of the controller also must be considered. It is usually desirable that the controller reacts rapidly to changes in the actual operating conditions without, however, having the tendency to overshoot; instability of operation should be avoided, for example due to excessively rapid response and consequent overshoot of the controller.